The Extending the business logic defined in a Model recipe showed how to extend methods defined on a model class. If you think about it, methods defined on the parent class of the model are also part of the model. This means that all the base methods
defined on models.Model (actually on models.BaseModel, which is the parent class of models.Model) are also available and can be extended.
This recipe shows how to extend create() and write() to control access to some fields of the records.